Ultrasonic cleaning typically involves immersing an item to be cleaned in a tank of cleaning liquid, then directing ultrasonic pressure waves into the tank. The pressure waves produce micro-cavitation in the liquid, which has a cleaning effect at the surface of the item to be cleaned.
In ultrasonic cleaning of this nature it is important to make good use of the ultrasound to increase efficiency. Problems can arise in distributing the ultrasonic pressure waves so that they are effective across the whole surface of the item to be cleaned, as standing waves linked to tank geometry can lead to the ultrasound in some parts of the tank being ineffective, and in other parts of the tank being too aggressive so as to potentially cause damage to the surface being cleaned.
There is a particular problem in providing an effective clean without damaging the surface which is being cleaned when the dirt on the surface is not evenly distributed and/or is composed of different types of material. For example, in cleaning surgical instruments before sterilisation, there may be various types of biological material on the instruments, in different sized clumps. For this type of cleaning application effective removal of large pieces of dirt is essential to guarantee that the sterilization process can be performed effectively.
Another problem encountered when trying to providing an effective clean is to enable a tank form that can be used for many cleaning operations without itself entrapping, retaining or entraining dirt from the item or items that are cleaned. For example, dead volumes, interstices or passageways in the tank may collect dirt in a way that then reduces the effectiveness of subsequent cleaning operations. For example, in a process of cleaning surgical instruments before sterilisation, there may be various types of biological material on the instruments, in different sized clumps, that are removed by cleaning from the surface of the instruments. However, this material may be transferred to and retained in the tank by a rack, mount, support or holder for the surgical instruments, or other features within the tank. For this type of cleaning application, effective removal of dirt from surfaces of the tank is desirable to increase the effectiveness of that the cleaning process from one cleaning operation to the next.
There is also a problem in providing effective drying without dirtying the surface which has been cleaned. For example, in cleaning surgical instruments before sterilisation, there may be various types of material on the instruments in the cleaning liquid that remain on the instruments when they are removed from the tank of cleaning liquid. For this type of cleaning application, effective removal of cleaning liquid is useful to enable the sterilization process to be performed effectively.
Example embodiments of the present invention aim to address one or more problems associated with the prior art, for example those problems set out above.